The invention relates to a process for the continuous fermentation of solutions, especially of grape juice.
Processes are known in the brewing and wine industry for continuously fermenting beer wort or grape juice, in which the unfermented wort or the grape juice of the grape mash is fed continuously to a fermentation vat.
A process for continuously fermenting solutions to yield products of fermentation or microorganisms is known from the Austrian Pat. No. 155,464. In this process, the fermentation takes place in one or more double-chamber receptacles, connected in series. The unfermented mash is introduced into one chamber and, while air is blown in and a suspension is maintained, is conducted towards the top thereof, where it can flow over into the second chamber of the receptacle and sink again to the bottom. A settling chamber is connected to the double-chamber receptacle, in which the fermented mash can come to rest, so that the microorganisms are concentrated under the influence of gravity in a portion of the exhausted fermentation liquor. Since the lower part of this settling chamber is in open connection with the lower end of the double-chamber receptacle, the yeast can again enter the double-chamber receptacle of the fermentation zone from below.
In addition, a process is known from the German Pat. No. 1,209,088, which comprises a hollow slender fermentation tower for beer brewing which has inlets at its lower end for unfermented wort and for air and which is connected at its upper end over an overflow with a product-discharge line, which in turn is connected with a yeast settling chamber. The fermentation tower is connected at its upper end with a vent, through which carbon dioxide can escape.
Concerning to the German Pat. No. 1,207,324, the process therein uses a tower-fermenter which is equipped with perforated distribution elements over its length which ensure a uniform distribution of the yeast in the wort or the mash.
A further development is reported in the German Pat. No. 1,322,793 where in addition it is proposed to install a pulsation unit to ensure a good distribution of the yeast.
U.S. Pat. No. 3,575,813 describes a continuous fermentation process where, in a fermentation tower, perforated bell-shaped plates are fixed to attain a good distribution of the yeast. The fermentation tower is fed from the top.
A fermentation unit equipped with diagonal arranged perforated baffles which turn the rising fermentation gases to realize a mixing effect of the reactants is known from the U.S. Pat. No. 3,413,124.
U.S. Pat. No. 4,009,286 discloses a wort fermentation with immobilized yeast and following enzymation under sterile conditions. To attain a continuously running fermentation it is necessary to install at least two reaction units, otherwise the system only allows batch-wise fermentation.
U.S. Pat. No. 3,234,026 proposes a continuously running wort fermentation by the installing of some agitator equipped vessels in one line.
U.S. Pat. No. 2,967,107 describes a fermentation system wherein some fermentation reactors equipped with special agitators are installed in one line.
With respect to U.S. Pat. No. 1,884,272 a system for culturing yeast in vats connected in series is described.
These previously known processes suffer from the common disadvantage that they represent a more or less open system, from which undesirable microorganisms, such as, for example, bacteria, cannot be entirely excluded, and thus changes may occur that could result in spoiling the products of the fermentation process, so that the suitability and the efficiency of these processes leave much to be desired.